The lamination of transparent films onto a side of a security paper substrate is known from International (PCT) Publications Nos. WO 2008/104904 A1, WO 2009/112989 A1 and WO 2010/001317 A1 in the name of the present Applicant, which publications are all incorporated herein by reference in their entirety.
Further improvements of these known solutions are required, especially with a view to create a transparent polymer window with a field of lenses in the security paper substrate.